Seasonal dam on Russian River goes up early amid growing call for water conservation

A seasonal dam on the Russian River started filling a month early, creating a recreational lagoon and boosting the water supply for 600,000 Sonoma and Marin county residents|

Citing scant rainfall and historically low reservoirs, Sonoma County water managers are inflating a rubber dam on the Russian River near Forestville a month earlier than usual.

They are also urging the public to conserve water, noting that the region is entering the arid summer and fall months after two of the driest rain seasons on record in the past 127 years.

Lake Sonoma northwest of Healdsburg, the region’s major water source, is at 62% of capacity, while Lake Mendocino near Ukiah is at 44% of targeted capacity — both all-time lows for this time of year.

“We want to keep as much water as possible (in the reservoirs),” said Barry Dugan, a Sonoma Water spokesman.

“The beginning and end of dry periods are unpredictable, so taking steps now to save water is the responsible approach to prepare for what may be a longer drought,” the Sonoma-Marin Saving Water Partnership website says.

The partnership represents 12 water utilities in the two North Bay counties.

With the wettest months and hopes for a “March miracle” now over, Santa Rosa has recorded 12.77 inches of rain since Oct. 1, more than 20 inches below average.

Dairy farmers and some rural residents have begun hauling water as their wells and ranch ponds go dry.

The seasonal dam on the lower Russian River is filled with water through opened valves. It plays a crucial role in providing water to more than 600,000 Sonoma and Marin county residents.

Filling started last week but is going slowly to avoid drawing too much water from the river, Dugan said.

On Wednesday, the flow at Hacienda was a paltry 107 cubic feet per second for springtime, and it must stay above 85 cfs to safeguard wildlife and water quality. “We can’t fill (the dam) too quickly,” Dugan said.

When full, the 11-foot dam made of heavy-duty rubber creates a lagoon upstream from the agency’s massive concrete fish ladder located below Wohler Bridge.

Water from the lagoon is pumped into four off-stream ponds that recharge the aquifer below wells that draw naturally purified water from deep sand and gravel beds near the river.

The dam usually goes up in May, but Dugan said “we’re ahead of the curve” due to dry conditions for a second straight year. Last year, filling the rubber dam began even earlier, in early March.

The dam reaching 175 feet across the river remains in place all summer and into the fall, with water spilling over the top and boaters required to portage around it.

The lagoon, which backs up to about Riverfront Regional Park, affords a flatwater stretch of river available for recreation, said David Robinson, Sonoma County Regional Parks park manager.

With the lack of moving water, afternoon winds pushing upriver can impact boating, he advised.

Low flows anticipated on the river this summer can require more portages over gravel bars and may also increase water temperature and the possibility of algal blooms, Robinson said.

Toxic blue-green algae have been cited in the deaths of three dogs on the river and in a Santa Rosa city park.

“With another year of drought, we are not expecting optimal recreation opportunities,” Robinson said.

Dugan at the water agency said it is too soon to tell what the summertime flow will be with state regulatory decisions pending.

“There will be less water in the river than a normal year,” he said. “We just don’t know how much.”

You can reach Staff Writer Guy Kovner at 707-521-5457 or On Twitter @guykovner.

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